A power semiconductor device is required to have both high breakdown voltage and low on-resistance, but in general, there is a trade-off relationship between a breakdown voltage and on-resistance of the device.
Among power field effect transistors (power MOS transistor) having a trench gate, a power MOS transistor having a field plate electrode buried in a trench and having a distribution of an impurity concentration in a direction from the bottom portion side to the upper side of the trench in a drift region where electrons travel is known.
By combining the trench type field plate electrode and the impurity concentration distribution of the drift region, the electric field distribution of the drift region is more uniform, and the trade-off between the breakdown voltage and on-resistance of an active region is improved.
However, when the impurity concentration distribution described above and the termination structure of the related art are combined, since the impurity concentration is constant in the longitudinal direction of the trench in the termination region, there is a problem that the same electric field distribution as the active region may not be obtained and the breakdown voltage of the termination region is decreased.